Question

(a) The number of new infections of HIV in one country was estimated in 2000 and 2018.
Table 4.1 shows the results.

(i) Calculate the percentage decrease in the number of new infections of HIV between 2000 and 2018 in Table 4.1.

(ii) Suggest three reasons for this decrease.

(iii) State the type of organism that causes the HIV disease.

(b) Fig. 4.1 is a photomicrograph of human blood.

i) Table 4.2 shows some information about the components of blood shown in Fig. 4.1.
Complete Table 4.2.

(ii) A student knows the actual size of the component labelled A in Fig. 4.1.
Describe how the student determines the magnification of the image of the component labelled A.

▶️Answer/Explanation

Ans:

4(a)(i) 280 – 170 / 110 ;

  ((110 / 280) × 100) = 39(.3) (%) ;

4(a)(ii) any three from:

ref to education / campaigns ;
increased, monitoring / testing ;
use of condoms / barrier contraception ;
increased abstinence ;
screening of blood transfusions ;
provision of clean needles / needle banks ;
reduction in sharing needles ;
reduced breast feeding by infected mothers
AVP ;

4(a)(iii) virus ;

4(b)(i) 

;;;;
one mark for each row

4(b)(ii) measure (with a ruler the image length of one of the red blood cells) ;
         divide this length by the actual size / magnification = image size / actual size ;